The neutral Higgs sector of the NMSSM consists in three complex scalars \(H_u^0\) , \(H_d^0\)  and \(S\)  where \(H_u^0\)  and \(H_d^0\)  are members of SU(2) doublets and \(S\)  is a gauge singlet [1]}, [2]}. Their self couplings originate from terms
\(W=\lambda {\cal H}_u {\cal H}_d {\cal S} + \frac{\kappa }{3} {\cal S}^3 + \dots \) 
